<ul data-eligibleForWebStory="true"><li>1. A Left Join followed by an Inner Join behaves like a regular Inner Join.</li><li>2. Avoid using groupBy/associateBy in the app layer when pagination is applied to ensure consistency.</li><li>3. Understand the SQL Query Execution Order: FROM → JOIN → WHERE → GROUP BY → HAVING → SELECT → ORDER BY.</li><li>4. Adding AND conditions in LEFT JOIN ON does not affect row count.</li><li>5. For one-to-one relationships, use '@OneToOne' and enforce a UNIQUE KEY in the database.</li><li>6. '@Transactional' only guarantees atomicity in specific situations.</li><li>7. WHERE vs HAVING: WHERE filters rows before grouping, while HAVING filters after grouping.</li><li>Consideration: Check and understand the actual SQL generated by JPA for better optimization.</li></ul>

Some Tips on SQL Usage in Spring

Discover more